1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly, to an apparatus for preventing reverse rotation of a scroll compressor capable of preventing a compressor from being driven in a direction opposite to a driving direction of compressing a fluid.
2. Description of the Background Art
In general, several types of compressor according to a compression method can be applied to various devices, and, for a small sized and lightweight air conditioning device, a scroll compressor is mainly used.
FIG. 1 is a sectional view of a scroll compressor according to the conventional art.
A scroll compressor according to the conventional art includes a casing 1 to which a suction port 11 through which a fluid is sucked and a discharging port 12 through which a compressed fluid is discharged are connected respectively, forming a certain close space; a driving unit (D) mounted at a lower portion of the casing 1, and generating a driving force; a compression unit (P) positioned at an upper portion of the casing 1 to compress a fluid sucked through the suction port 11 and discharge the compressed fluid through the discharging port 12, using a rotational force of a rotational shaft 23, which is generated by the driving force of the driving unit (D).
A main frame 2 for supporting the compression unit (P), and supporting one end of the rotational shaft 23 to make rotation of the rotary shaft 23 possible, is installed at an upper portion of the casing 1. A lower frame 3 for rotatably supporting the other end of the rotational shaft 23 is installed at a lower portion of the casing 1.
The driving unit (D) includes a stator 4 mounted in the casing 1, and a rotor 5 rotatably inserted at the inside of the stator 4, and, at the inside of the rotor 5, the rotational shaft 23 is pressed and inserted. The rotational shaft 23 includes a shaft portion 20 having a certain length, and pressed and inserted at the rotor 5, and an eccentric portion 21 formed at one end of the shaft portion 20 to be eccentric from the center of the shaft portion 20, and connected with the compression unit (P).
The compression unit (P) includes a fixed scroll 7 fixedly coupled with the main frame 2, and an orbiting scroll 8 meshed with the fixed scroll 7, and also coupled with the rotational shaft 23. A slide bush 6 is inserted at a lower portion of the orbiting scroll 8, and the eccentric portion 21 of the rotational shaft 23 is inserted to be coupled with the slide bush 6. A suction hole 7a through which gas, which has passed through the suction pipe 11, is flown into a compression space formed between the orbiting scroll 8 and the fixed scroll 7, is formed at one side of the fixed scroll 7. At an upper portion of the fixed scroll 7, a discharging hole 7b through which compressed gas is discharged, is formed, and, at an upper side of the discharging hole 7b, a check valve (not shown) for preventing the discharged fluid from flowing backward, is installed. An Oldham ring 9 for preventing self-rotation of the orbiting scroll 8 is installed between the orbiting scroll 8 and the main frame 2. At an upper surface of the fixed scroll 7, a dividing plate 10 for dividing the inside of the casing 1 into a low pressure area (N) and a high pressure area (M), is installed.
FIG. 2 is a disassembled perspective view showing a slide bush and an eccentric portion of a rotational shaft according to the conventional art.
As shown therein, the eccentric portion 21 of the rotational shaft has a cylindrical form with a certain length. At an outer circumference thereof, a first and second outer planes 23a and 23b are formed so as to be parallel with or have a predetermined angle on the basis of a reference line connecting the center of the shaft portion 20 of the rotational shaft and the center of the eccentric portion 21, and outer circumferential surfaces 24a and 24b connecting the first and second outer planes 23a and 23b are formed.
Also, the slide bush 6 has a cylindrical form with a certain length, and an inserting hole 40 penetrates the inside of the slide bush 6 so that the eccentric portion 21 of the rotational shaft can be inserted therein at a variable gap therebetween. At an inner circumferential surface of the suction hole 40, a first and second inner planes 26a and 26b are formed so as to confront with the first and second outer plane 23a and 23b formed at the outer circumferential surface of the eccentric portion 21 of the rotational shaft respectively.
Operations of the conventional scroll compressor configured as above will now be described.
When power is applied to a stator 4, a rotor 5 rotates by an electromagnetic interaction of the stator 4 and the rotor 5, and a rotational shaft 23 fixed at the rotor 5 rotates forwardly. At this time, one of the first and second outer planes 23a and 23b, which is formed toward a forward rotation direction on the basis of the reference line connecting the axis of the shaft portion 20 of the rotational shaft 23 and the axis of the eccentric portion 21 thereof is in contact with one of the first and second inner planes 26a and 26b of the inner circumferential surface of the inserting hole 40 of the slide bush 6. Through this contact of the planes, the rotational force of the rotational shaft 23 is transmitted to the slide bush 6, and, after all, transmitted to the orbiting scroll 8 inserted at and connected with an outer circumferential surface of the slide bush 6. At this time, the orbiting scroll 8 starts to orbit.
A fluid sucked through the suction port 11 by the interaction of the orbiting scroll 8, which is orbiting, and the fixed scroll 7, is compressed and discharged to the outside.
At this time, a check valve (not shown) installed at the discharging hole 7b prevents the fluid, which has been discharged to a high pressure area (M) through the discharging hole 7b, from flowing backward to the low pressure area (N).
However, to the conventional scroll compressor above, several apparatuses for preventing reverse rotation is applied in order to prevent damage of the compressor, which is caused by the reverse rotation generated by the following reasons, but there are still remained problems below.
In case of applying a single-phase motor as a driving unit for generating a rotational force, if a load generated during an operation of the compressor becomes greater than a motor torque, a rotational force of a motor is reduced, further, the motor is rotated reversely, and thus, the orbiting scroll is rotated reversely. Accordingly, an abnormal oscillation and noise of the compressor are generated, and reliability of the compressor is deteriorated.
Also, in case of applying a three-phase motor as a driving unit for generating a rotational force, if wiring of a motor is not right, and so supply power is changed, the motor is rotated reversely, and thus the compressor is damaged. In order to solve this problem, a reversed-phase preventing circuit is attached. When the phase of the supply power is changed, the reverse-phase preventing circuit turns off power supplied to the compressor so that the compressor cannot be operated, and thus protects the compressor. However, since, in installing the circuit, expenses are increased, and there still exists a possibility for the compressor to be ill-operated according to a complicated configuration, reliability of the compressor is deteriorated.
Also, there is a method applying a single direction clutch structure between the rotational shaft 23 and a lower frame 3, but in this case, expenses for installing is increased too. Also, since a roller portion of a clutch has to be continuously operated therewith even in a normal operation, damage of power is generated whereby efficiency is deteriorated, and noise is generated too by an unnecessary movement.